1. Field of the Invention
The present invention relates generally to devices used to lubricate the fifth wheel of a trailer, and more particularly to a device especially adapted for lubricating the fifth wheel without disconnecting the trailer from the truck.
2. Description of tile Prior Art
Devices designed to lubricate the sliding connection between a trailer and a truck, known as the fifth wheel, are well known. For example, the following U.S. patents disclose devices for lubrication of the fifth wheel U.S. Pat. Nos. 3,622,173; 3,743,054; 4,541,651; 4,802,554; and 4,913,263. More specifically, U.S. Pat. No. 3,622,173 discloses a fifth wheel that contains it own grease reservoir. Although it is a good idea to have a supply of grease available to the fifth wheel, the administration of the grease is not controlled by positive pressure. In this respect, it would be desirable if a fifth wheel lubrication device were provided that administers grease with positive pressure.
U.S. Pat. No. 3,743,054 discloses a fifth wheel which includes a source of positive pressure for administering grease to the fifth wheel. The source of positive pressure is a cylinder installed next to the fifth wheel that is manually operable. Although it is desirable to administer grease to the fifth wheel under positive pressure, it is undesirable to require manual administration of the grease. Inclement weather conditions and discomfort to an operator can both make it quite inconvenient to manually administer the grease to the fifth wheel. In this respect, it would be desirable if a fifth wheel lubrication device were provided that did not require manual administration of grease to the fifth wheel. Moreover, it would also be desirable if a fifth wheel lubrication device were provided that did not require the user to be exposed to inclement weather as the lubrication device is used.
U.S. Pat. No. 4,541,651 discloses a fifth wheel lubrication system that automatically supplies grease to the fifth wheel under a pressure exerted by a hydrostatic head of grease from an elevated grease reservoir. A disadvantage of this device is that as the grease supply is depleted, the hydrostatic head lessens. Eventually, when the hydrostatic head decreases enough, essentially no pressure is exerted on the grease to permeate the fifth wheel. In this respect, it would be desirable if a fifth wheel lubrication device were provided that did not depend on the continually lessening pressure exerted by a continually lessening hydrostatic head.
U.S. Pat. No. 4,913,263 discloses rupturable grease packets for lubricating fifth wheels. The size of the grease packet is very limited. Moreover, once the packets are ruptured, they are not replenishable. In this respect, it would be desirable if a fifth wheel lubrication device were provided which did not use rupturable, unreplenishable packets.
U.S. Pat. No. 4,802,554 may be of interest for a grease applying method which employs a rotating part that mechanically picks up a quantity of grease and wipes the grease up against a surface to be greased. One disadvantage of using this device with a fifth wheel is that this device requires quite a number of moving parts and would be very inconvenient to install and operate in the vicinity of the fifth wheel. In this respect, it would be desirable if a fifth wheel lubrication device were provided which adequately lubricated the fifth wheel without employing a lot of moving parts.
There are certain specific driving conditions in which it would be desirable to add grease to the fifth wheel. Such conditions include driving around curves, making turns, and backing up. In this respect, it would be desirable if a fifth wheel lubrication device were provided that permitted addition of grease to the fifth wheel as the truck and trailer go around curves, make turns, and backing up.
The fifth wheel presents a relatively large surface requiring lubrication. If a lubricant is applied unevenly to the surface, then inadequate lubrication may occur. In this respect, it would be desirable if there were a fifth wheel lubrication device which provided for a substantially even supply of lubricant to the fifth wheel.
To avoid problems of inclement weather and to be able to apply lubricant to the fifth wheel even as the rig is being driven, it would be desirable if a fifth wheel lubrication device were controllable from inside the cab of the truck. In that positive pressure is desirable over gravity flow for administering lubricant to the fifth wheel, it would be desirable if administration of lubricant to the fifth wheel were controlled by a source of positive pressure that was controllable from inside the truck.
Most trucks, especially ones with air brakes, have on board air pumps. In this respect, it would be desirable if a fifth wheel lubrication device were provided which utilized an on board air pump to power the lubrication device.
Lubrication devices for fifth wheels of trailers have a common characteristic with many lubrication devices. That is, they can run out of lubricant without a user being aware of the lubricant depleted status. In this respect, it would be desirable if a fifth wheel ;lubrication device were provided which provided a signal that indicated a low level of lubricant in a lubricant supply.
Thus, while the foregoing body of prior art indicates it to be well known to use lubrication devices for a fifth wheel of a trailer, the prior art described above does not teach or suggest a trailer fifth wheel lubrication apparatus which has the following combination of desirable features: (1) administers grease with positive pressure; (2) does not require manual administration of grease to the fifth wheel; (3) does not use rupturable, unreplenishable grease-containing packets; (4) does not depend on the continually lessening pressure exerted by a continually lessening hydrostatic head; (5) adequately lubricates the fifth wheel without employing a lot of moving parts; (6) does not require the user to be exposed to inclement weather as the lubrication device is used; (7) permits addition of grease to the fifth wheel as the truck and trailer go around curves, make turns, and are backed up; (8) provides for a substantially even supply of lubricant to the fifth wheel; (9) is controllable from inside the cab of the truck; (10) administers lubricant to the fifth wheel by means of a source of positive pressure that is controllable from inside the truck; (11) utilizes an on board air pump to power the lubrication device; and (12) provides a signal that indicates a low level of lubricant in a lubricant supply. The foregoing desired characteristics are provided by the unique trailer fifth wheel lubrication apparatus of the present invention as will be made apparent from the following description thereof. Other advantages of the present invention over the prior art also will be rendered evident.